Discrete carbon nanotubes with targeted oxidation levels and stable gel formulations thereof

ABSTRACT

Discrete, individualized carbon nanotubes having targeted, or selective, oxidation levels and/or content on the interior and exterior of the tube walls are claimed. Such carbon nanotubes can have little to no inner tube surface oxidation, or differing amounts and/or types of oxidation between the tubes&#39; inner and outer surfaces. These new discrete carbon nanotubes are useful in plasticizers, which can then be used as an additive in compounding and formulation of elastomeric, thermoplastic and thermoset composite for improvement of mechanical, electrical and thermal properties.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. Ser. No. 13/164,456, filed Jun. 20,2011, and its progeny; and U.S. Ser. No. 13/140,029, filed Aug. 9, 2011,and its progeny, the disclosures of each of which is incorporated hereinby reference. This application claims priority to US ProvisionalApplication No. 62/319,599, filed Apr. 7, 2016 and is a divisional ofSer. No. 15/730,284 filed on Oct. 11, 2017 which was acontinuation-in-part from US non-provisional application Ser. No.15/482,304, filed Apr. 7, 2017, the disclosures of each of which isincorporated herein by reference.

FIELD OF INVENTION

The present invention is directed to novel discrete carbon nanotubecompositions having targeted oxidation levels and/or content, andformulations thereof, such as with plasticizers, elastomers or rubbercompounds.

BACKGROUND AND SUMMARY OF THE INVENTION

Carbon nanotubes can be classified by the number of walls in the tube,single-wall, double wall and multiwall. Carbon nanotubes are currentlymanufactured as agglomerated nanotube balls, bundles or forests attachedto substrates. Use of carbon nanotubes as a reinforcing agent inelastomeric, thermoplastic or thermoset polymer composites is an area inwhich carbon nanotubes are predicted to have significant utility.However, utilization of carbon nanotubes in these applications has beenhampered due to the general inability to reliably produce individualizedcarbon nanotubes and the ability to disperse the individualized carbonnanotubes in a polymer matrix. Bosnyak et al., in various patentapplications (e.g., US 2012-0183770 A1 and US 2011-0294013 A1), havemade discrete carbon nanotubes through judicious and substantiallysimultaneous use of oxidation and shear forces, thereby oxidizing boththe inner and outer surface of the nanotubes, typically to approximatelythe same oxidation level on the inner and outer surfaces, resulting inindividual or discrete tubes.

The present invention differs from those earlier Bosnyak et al.applications and disclosures. The present invention describes acomposition of discrete, individualized carbon nanotubes havingtargeted, or selective, oxidation levels and/or content on the exteriorand/or interior of the tube walls. Such novel carbon nanotubes can havelittle to no inner tube surface oxidation, or differing amounts and/ortypes of oxidation between the tubes' inner and outer surfaces. Thesenew discrete tubes are useful in many applications, includingplasticizers, which can then be used as an additive in compounding andformulation of elastomeric, thermoplastic and thermoset composite forimprovement of mechanical, electrical and thermal properties.

One embodiment of the present invention is a composition comprising aplurality of discrete carbon nanotubes, wherein the discrete carbonnanotubes comprise an interior and exterior surface, each surfacecomprising an interior surface oxidized species content and an exteriorsurface oxidized species content, wherein the interior surface oxidizedspecies content differs from the exterior surface oxidized speciescontent by at least 20%, and as high as 100%, preferably wherein theinterior surface oxidized species content is less than the exteriorsurface oxidized species content.

The interior surface oxidized species content can be up to 3 weightpercent relative to carbon nanotube weight, preferably from about 0.01to about 3 weight percent relative to carbon nanotube weight, morepreferably from about 0.01 to about 2, most preferably from about 0.01to about 1. Especially preferred interior surface oxidized speciescontent is from zero to about 0.01 weight percent relative to carbonnanotube weight.

The exterior surface oxidized species content can be from about 1 toabout 6 weight percent relative to carbon nanotube weight, preferablyfrom about 1 to about 4, more preferably from about 1 to about 2 weightpercent relative to carbon nanotube weight. This is determined bycomparing the exterior oxidized species content for a given plurality ofnanotubes against the total weight of that plurality of nanotubes.

The interior and exterior surface oxidized species content totals can befrom about 1 to about 9 weight percent relative to carbon nanotubeweight.

Another embodiment of the invention is a composition comprising aplurality of discrete carbon nanotubes, wherein the discrete carbonnanotubes comprise an interior and exterior surface, each surfacecomprising an interior surface and an exterior surface oxidized speciescontent, wherein the interior surface oxidized species content comprisesfrom about 0.01 to less than about 1 percent relative to carbon nanotubeweight and the exterior surface oxidized species content comprises morethan about 1 to about 3 percent relative to carbon nanotube weight.

Another embodiment of the invention is a stable gel consisting ofdiscrete carbon nanotubes, wherein the discrete carbon nanotubes areindividually coated with water, oils, waxes, nitric acid, or sulfuricacid. This coating prevents the formation of Van der Waals, electrical,or electrostatic forces between the discrete carbon nanotubes, therebypreventing the carbon nanotubes from agglomerating. In some embodiments,the gel may comprise as much as 99% coating material and as little as 1%carbon nanotubes by weight. In other embodiments, the gel may contain asmuch as 2% CNTs, or as much as 3% CNTs, or as much as 5% CNTs, or asmuch as 7% CNTs, or as much as 10% CNTs, or as much as 15% CNTs, or asmuch as 25% CNTs by weight. Removing the water or other coating materialfrom the gel by drying would lead to the formation of anhydride, Van derWaals, electrostatic, or other bonds between the carbon nanotubes. Theformation of these bonds would lead to the CNTs re-agglomerating andceasing to be discrete carbon nanotubes. Surprisingly, the use ofsurfactants is not typically required in the formation of the disclosedgels and thus there is little to no surfactant contained within the gel.This allows the incorporation of discrete carbon nanotubes into a matrixwithout the use of a surfactant which may reduce the connectivity orcrosslinking of the matrix or otherwise interfere with the desiredmechanical properties of the matrix.

The discrete carbon nanotubes of any composition embodiment abovepreferably comprise a plurality of open ended tubes, more preferably theplurality of discrete carbon nanotubes comprise a plurality of openended tubes. The discrete carbon nanotubes of either compositionembodiment above are especially preferred wherein the inner and outersurface oxidation difference is at least about 0.2 weight percent.

The compositions described herein can be used as an ion transport.Various species or classes of compounds/drugs/chemicals whichdemonstrate this ion transport effect can be used, including ionic, somenon-ionic compounds, hydrophobic or hydrophilic compounds.

The new carbon nanotubes disclosed herein are also useful in groundwater remediation.

The compositions comprising the novel discrete targeted oxidized carbonnanotubes and also be used as a component in, or as, a sensor.

The compositions disclosed herein can also be used as a component in, oras, drug delivery or controlled release formulations.

The compositions disclosed herein may be used as a structuralscaffolding for catalysts. As discussed, catalysts, enzymes, proteins,peptides or other small or large molecules may be attached to theexterior of the disclosed carbon nanotubes. The disclosed nanotubescaffolding may be useful for positioning the attached catalysts withina matrix, positioning multiple catalytic proteins or molecules withrespect to each other.

Carbon nanotube scaffolding may be created by attaching a ligand orconnecting molecule to the exterior surface of a group of discretecarbon nanotubes and attaching a complimentary receptor or bindingmolecule to the exterior surface of a second group of discrete carbonnanotubes. If these two groups of nanotubes are dispersed, theconnecting and complimentary binding molecules will be allowed to bindto each other, thereby indirectly connecting the nanotubes to which theconnecting and bind molecules were attached Examples of suchcomplimentary molecules include complimentary strands of DNA or RNA,proteins, peptides, large molecules and/or small molecules which bind orconnect to complimentary receiving or binding molecules.

In some embodiments complimentary molecules will be attached to theexterior surface of two groups of discrete carbon nanotubes such thatwhen the two groups of discrete complimentary nanotubes are dispersedwithin the same solution, a 3D scaffold of carbon nanotubes may form or,in some cases, self-assemble as the attached complimentary moleculesbind to each other. Tailoring of the complimentary molecules attached tothe carbon nanotubes may be used to adjust the physical, chemical,and/or electrical properties of the resulting carbon nanotube network.

In addition to the described complementary molecules described above,catalysts, drugs, peptides, medicines, magnetic particles, or otherdesired large and/or small molecules may be attached to the exteriorsurface of the carbon nanotubes forming the described scaffold network.This may allow for the concentration, localization, and/or targeteddelivery of the desired molecule to a specific location within a matrixor within a patient.

In some embodiments, the compositions disclosed herein can be used as acomponent in, or as, payload molecule delivery or drug delivery orcontrolled release formulations. In particular various drugs, includingsmall molecule therapeutics, peptides, nucleic acids, or combinationsthereof may be loaded onto nanotubes and delivered to specificlocations. Discrete carbon nanotubes may be used to help smallmolecules/peptides/nucleic acids that are cell membrane impermeable orotherwise have difficulty crossing the cell membrane to pass through thecell membrane into the interior of a cell. Once the smallmolecule/peptide/nucleic acid has crossed the cell membrane, it maybecome significantly more effective. Small molecules are defined hereinas having a molecular weight of about 500 Daltons or less.

The pro-apoptotic peptide KLAKLAK is known to be cell membraneimpermeable. By loading the peptide onto discrete carbon nanotubesKLAKLAK is able to cross the cell membrane of LNCaP human prostatecancer cells and trigger apoptosis. The KLAKLAK-discrete carbon nanotubeconstruct can lead to the apoptosis of up to 100% of targeted LNCaPhuman prostate cancer cells. Discrete carbon nanotubes may also beuseful for delivering other small molecules/peptides/nucleic acidsacross the cell membranes of a wide variety of other cell types.Discrete carbon nanotubes may be arranged to have a high loadingefficiency, thereby enabling the delivery of higher quantities of drugsor peptides. In some instances, this transport across the cell membranemay be accomplished without the need for targeting or permeationmoieties to aid or enable the transport. In other instances, thediscrete carbon nanotubes may be conjugated with a targeting moiety (ex.peptide, chemical ligand, antibody) in order to assist with thedirection of a drug or small molecule/peptide/nucleic acid towards aspecific target. Discrete carbon nanotubes alone are well tolerated anddo not independently trigger apoptosis.

Peptides, small molecules, and nucleic acids and other drugs may beattached to the exterior of the discrete carbon nanotubes via Van derWaals, ionic, or covalent bonding. As discussed, the level of oxidationmay be controlled in order to promote a specific interaction for a givendrug or small molecule/peptide/nucleic acid. In some instances, drugs orpeptides that are sufficiently small may localize to the interior ofdiscrete carbon nanotubes. The process for filling the interior ordiscrete carbon nanotubes may take place at many temperatures, includingat or below room temperature. In some instances, the discrete carbonnanotubes may be filled to capacity in as little as 60 minutes with bothsmall and large molecule drugs.

The payload molecule can be selected from the group consisting of a drugmolecule, a radiotracer molecule, a radiotherapy molecule, diagnosticimaging molecule, fluorescent tracer molecule, a protein molecule, andcombinations thereof.

Exemplary types of payload molecules that may be covalently ornon-covalently associated with the discrete functionalized carbonnanotubes disclosed herein may include, but are not limited to, protonpump inhibitors, H2-receptor antagonists, cytoprotectants, prostaglandinanalogues, beta blockers, calcium channel blockers, diuretics, cardiacglycosides, antiarrhythmics, anti angina's, vasoconstrictors,vasodilators, ACE inhibitors, angiotensin receptor blockers, alphablockers, anticoagulants, antiplatelet drugs, fibrinolytics,hypolipidemic agents, statins, hypnotics, antipsychotics,antidepressants, monoamine oxidase inhibitors, selective serotoninreuptake inhibitors, antiemetics, anticonvulsants, anxiolytic,barbiturates, stimulants, amphetamines, benzodiazepines, dopamineantagonists, anti histanhines, cholinergics, anticholinergics, emetics,cannabinoids, 5-HT antagonists, NSAIDs, opioids, bronchodilator,antiallergics, mucolytics, corticosteroids, beta-receptor antagonists,anticholinergics, steroids, androgens, antiandrogens, growth hormones,thyroid hormones, anti-thyroid drugs, vasopressin analogues,antibiotics, antifungals, antituberculous drugs, antimalarials,antiviral drugs, anti protozoal drugs, radioprotectants, chemotherapydrugs, cytostatic drugs, and cytotoxic drugs such as paclitaxel.

Magnetic particles may be bound or attached to the carbon nanotubesdisclosed herein. The bound magnetic particles may be used to influencethe orientation, location, or position of the carbon nanotube to whichthe magnetic particle is attached. Applying a magnetic field to carbonnanotubes bound to magnetic particles may allow the carbon nanotube tobe moved to a particular location. Magnetic fields may be generated bynatural magnets or electro-magnetic devices including at least, MRI,fMRI, or pulsed electromagnetic field generator devices. Additionally, asingle magnetic field generation device may be utilized or multiplemagnetic field generation devices may be used. In some embodiments, anarray of EMF generators may be used to move CNTs bound to magneticparticles and/or cause such CNTs to vibrate, rotate, oscillate, or todirect CNTs from one specific position to another.

More than one species of magnetic particle may be bound to a singlecarbon nanotube. In some embodiments, the distinct species of magneticparticle may behave differently in the same magnetic field, thuscreating an increased variety of possibilities for impacting thebehavior of carbon nanotubes attached to more than one species ofmagnetic particle.

Magnetic particles bound to carbon nanotubes may comprise approximately0.001 weight percent relative to carbon nanotube weight, or may compriseapproximately 0.01 weight percent relative to carbon nanotube weight, ormay comprise approximately 0.1 weight percent relative to carbonnanotube weight, or may comprise approximately 1 weight percent relativeto carbon nanotube weight, or may comprise approximately 10. weightpercent relative to carbon nanotube weight.

Carbon nanotubes bound to magnetic particles may additionally contain apayload molecule as discussed above or have peptides, small molecules,nucleic acids, or other drugs or molecules attached to their exterior.These combinations may allow the nanotube, along with its associatedpayload or substantially non-magnetic attached molecule to be directedto a particular location where the payload molecule of the attachedmolecule may be desired. In this manner, targeted molecules could bedelivered to a particular location using a controlled magnetic field.

In some embodiments, magnetic fields may be used in order to flex ordistort discrete carbon nanotubes or a network, matrix, or scaffold ofdiscrete carbon nanotubes. If an open ended, payload carrying nanotubeis flexed or distorted as described, this may increase the rate at whichthe interior payload molecule is emptied into the surroundingenvironment thereby enabling the controlled, targeted, and/or timedrelease of payload molecules. Similarly, the described flexing of anetwork of carbon nanotubes may increase the rate at which payloadmolecules are loaded into the interior of open ended nanotubes or allowmolecules to be entrapped within the interior spaces of the nanotubenetwork itself while remaining external to any particular nanotube.

Batteries comprising the compositions disclosed herein are also useful.Such batteries include lithium, nickel cadmium, or lead acid types.

Formulations comprising the compositions disclosed herein can furthercomprise an epoxy, a polyurethane, or an elastomer. Such formulationscan be in the form of a dispersion. The formulations can also includenanoplate structures.

The compositions can further comprise at least one hydrophobic materialin contact with at least one interior surface.

The present invention relates to a composition comprising a plurality ofdiscrete carbon nanotubes and a plasticizer wherein the discrete carbonnanotubes have an aspect ratio of 10 to about 500, and wherein thecarbon nanotubes are functionalized with oxygen species on theiroutermost wall surface. The discrete carbon nanotubes comprise aninterior and exterior surface, each surface comprising an interiorsurface and exterior surface oxidized species content wherein theinterior surface oxidized species content comprises from about 0.01 toless than about 1 percent relative to carbon nanotube weight and theexterior surface oxidized species content comprises more than about 1 toabout 3 percent relative to carbon nanotube weight. The oxygen speciescan comprise carboxylic acids, phenols, or combinations thereof.

The composition can further comprise a plasticizer selected from thegroup consisting of dicarboxylic/tricarboxylic esters, timellitates,adipates, sebacates, maleates, glycols and polyethers, polymericplasticizers, bio-based plasticizers and mixtures thereof. Thecomposition can comprise plasticizers comprising a process oil selectedfrom the group consisting of naphthenic oils, paraffin oils, parabenoils, aromatic oils, vegetable oils, seed oils, and mixtures thereof.

The composition can further comprise a plasticizer selected from thegroup of water immiscible solvents consisting of but not limited tozylene, pentane, methylethyle ketone, hexane, heptane, ethyl actetate,ethers, dicloromethane, dichloroethane, cyclohexane, chloroform, carbontetrachloride, butyl acetate butanol, benzene or mixtures thereof.

In yet another embodiment the composition is further comprises aninorganic filler selected from the group consisting of silica,nano-clays, carbon black, graphene, glass fibers, and mixtures thereof.

In another embodiment the composition is in the form of free flowingparticles.

In another embodiment, the composition comprises a plurality of discretecarbon nanotubes and a plasticizer wherein the discrete carbon nanotubescomprise from about 10 weight percent to about 90 weight percent,preferably 10 weight percent to 40 weight percent, most preferably 10 to20 weight percent.

An another embodiment is a process to form a composition comprisingdiscrete carbon nanotubes in a plasticizer comprising the steps of: a)selecting a plurality of discrete carbon nanotubes having an averageaspect ratio of from about 10 to about 500, and an oxidative speciescontent total level from about 1 to about 15% by weight, b) suspendingthe discrete carbon nanotubes in an aqueous medium (water) at a nanotubeconcentration from about 1% to about 10% by weight to form an aqueousmedium/nanotube slurry, c) mixing the carbon nanotube/aqueous medium(e.g., water) slurry with at least one plasticizer at a temperature fromabout 30° C. to about 100° C. for sufficient time that the carbonnanotubes migrate from the water to the plasticizer to form a wetnanotube/plasticizer mixture, e) separating the water from the wetcarbon nanotube/plasticizer mixture to form a dry nanotube/plasticizermixture, and f) removing residual water from the drynanotube/plasticizer mixture by drying from about 40° C. to about 120°C. to form an anhydrous nanotube/.plasticizer mixture .

Another embodiment is the composition of discrete carbon nanotubes in aplasticizer further mixed with a least one rubber. The rubber can benatural or synthetic rubbers and is preferably selected from the fromthe group consisting of natural rubbers, polyisobutylene, polybutadieneand styrene-butadiene rubber, butyl rubber, polyisoprene,styrene-isoprene rubbers, styrene-isoprene rubbers, ethylene, propylenediene rubbers, silicones, polyurethanes, polyester-polyethers,hydrogenated and non-hydrogenated nitrile rubbers, halogen modifiedelastomers, flouro-elastomers, and combinations thereof.

Another embodiment is the composition of discrete carbon nanotubes in aplasticizer further mixed with at least one thermoplastic polymer or atleast one thermoplastic elastomer. The thermoplastic can be selectedfrom but is not limited to acrylics, polyamides, polyethylenes,polystyrenes, polycarbonates, methacrylics, phenols, polypropylene,polyolefins, such as polyolefin plastomers and elastomers, EPDM, andcopolymers of ethylene, propylene and functional monomers.

Yet another embodiment is the composition of discrete carbon nanotubesin a plasticizer further mixed with at least one thermoset polymer,preferably an epoxy, or a polyurethane. The thermoset polymers can beselected from but is not limited to epoxy, polyurethane, or unsaturatedpolyester resins.

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionsdescribing specific embodiments of the disclosure.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, certain details are set forth such asspecific quantities, sizes, etc., so as to provide a thoroughunderstanding of the present embodiments disclosed herein. However, itwill be evident to those of ordinary skill in the art that the presentdisclosure may be practiced without such specific details. In manycases, details concerning such considerations and the like have beenomitted inasmuch as such details are not necessary to obtain a completeunderstanding of the present disclosure and are within the skills ofpersons of ordinary skill in the relevant art.

While most of the terms used herein will be recognizable to those ofordinary skill in the art, it should be understood, however, that whennot explicitly defined, terms should be interpreted as adopting ameaning presently accepted by those of ordinary skill in the art. Incases where the construction of a term would render it meaningless oressentially meaningless, the definition should be taken from Webster'sDictionary, 3rd Edition, 2009. Definitions and/or interpretations shouldnot be incorporated from other patent applications, patents, orpublications, related or not.

Functionalized carbon nanotubes of the present disclosure generallyrefer to the chemical modification of any of the carbon nanotube typesdescribed hereinabove. Such modifications can involve the nanotube ends,sidewalls, or both. Chemical modifications may include, but are notlimited to covalent bonding, ionic bonding, chemisorption,intercalation, surfactant interactions, polymer wrapping, cutting,solvation, and combinations thereof. In some embodiments, the carbonnanotubes may be functionalized before, during and after beingexfoliated.

In various embodiments, a plurality of carbon nanotubes is disclosedcomprising single wall, double wall or multi wall carbon nanotube fibershaving an aspect ratio of from about 10 to about 500, preferably fromabout 40 to about 200, and an overall (total) oxidation level of fromabout 1 weight percent to about 15 weight percent, preferably from about1 weight percent to about 10 weight percent, more preferably from about1 weight percent to 5 weight percent, more preferably from about 1weight percent to 3 weight percent. The oxidation level is defined asthe amount by weight of oxygenated species covalently bound to thecarbon nanotube. The thermogravimetric method for the determination ofthe percent weight of oxygenated species on the carbon nanotube involvestaking about 7-15 mg of the dried oxidized carbon nanotube and heatingat 5° C/minute from 100 degrees centigrade to 700 degrees centigrade ina dry nitrogen atmosphere. The percentage weight loss from 200 to 600degrees centigrade is taken as the percent weight loss of oxygenatedspecies. The oxygenated species can also be quantified using Fouriertransform infra-red spectroscopy, FTIR, particularly in the wavelengthrange 1730-1680 cm⁻¹.

The carbon nanotubes can have oxidation species comprising carboxylicacid or derivative carbonyl containing species and are essentiallydiscrete individual nanotubes, not entangled as a mass. Typically, theamount of discrete carbon nanotubes after completing the process ofoxidation and shear is by a far a majority (that is, a plurality) andcan be as high as 70, 80, 90 or even 99 percent of discrete carbonnanotubes, with the remainder of the tubes still partially entangled insome form. Complete conversion (i.e., 100 percent) of the nanotubes todiscrete individualized tubes is most preferred. The derivative carbonylspecies can include phenols, ketones, quaternary amines, amides, esters,acyl halogens, monovalent metal salts and the like, and can vary betweenthe inner and outer surfaces of the tubes.

For example, one type of acid can be used to oxidize the tubes exteriorsurfaces, followed by water washing and the induced shear, therebybreaking and separating the tubes. If desired, the formed discretetubes, having essentially no (or zero) interior tube wall oxidation canbe further oxidized with a different oxidizing agent, or even the sameoxidizing agent as that used for the tubes' exterior wall surfaces at adifferent concentration, resulting in differing amounts—and/or differingtypes—of interior and surface oxidation.

As-made carbon nanotubes using metal catalysts such as iron, aluminum orcobalt can retain a significant amount of the catalyst associated orentrapped within the carbon nanotube, as much as five weight percent ormore. These residual metals can be deleterious in such applications aselectronic devices because of enhanced corrosion or can interfere withthe vulcanization process in curing elastomer composites. Furthermore,these divalent or multivalent metal ions can associate with carboxylicacid groups on the carbon nanotube and interfere with the discretizationof the carbon nanotubes in subsequent dispersion processes. In otherembodiments, the oxidized carbon nanotubes comprise a residual metalconcentration of less than about 10000 parts per million, ppm, andpreferably less than about 5000 parts per million. The metals can beconveniently determined using energy dispersive X-ray spectroscopy orthermogravimetric methods.

The composition of discrete carbon nanotubes in a plasticizer can beused as an additive to a variety of compounds and composites to improvethe mechanical properties, thermal and electrical conductivity. Anexample is as an additive in rubber compounds used to fabricate rubbercomponents in oil field applications such as seals, blowout preventersand drill motors with improved wear resistance, tear strength andthermal conductivity. Another example is as an additive in rubbercompounds used to fabricate tires, seals and vibration dampeners. Byselecting the appropriate plasticizer the additive has utility incompounding and formulating in thermoplastics, thermosets andcomposites.

As manufactured carbon nanotubes are in the form of bundles or entangledagglomerates and can be obtained from different sources, such as CNanoTechnology, Nanocyl, Arkema, and Kumho Petrochemical, to make discretecarbon nanotubes. An acid solution, preferably nitric acid solution atgreater than about 60 weight % concentration, more preferably above 65%nitric acid concentration, can be used to prepare the carbon nanotubes.Mixed acid systems (e. g. nitric and sulfuric acid) as disclosed in US2012-0183770 A1 and US 2011-0294013 A1, the disclosures of which areincorporated herein by reference, can be used to produce discrete,oxidized carbon nanotubes from as-made bundled or entangled carbonnanotubes.

A stable gel or wet cake comprising discrete carbon nanotubes maycontain between 1 and 20 percent solids by weight. Preferably between 2and 15 percent by weight and more preferably between 3 and 7 percent byweight. Some embodiments of the disclosed stable gel will containbetween 5 and 6 percent total solids by weight. The discrete carbonnanotubes contained in the described stable gel may include any of thevarious properties described herein including the oxidized and/or openedended carbon nanotubes described above. In some embodiments, thenanotubes contained in a stable gel will have a difference in thesurface oxidation of the inner and outer surfaces of at least about 0.2weight percent. In some embodiments, the nanotubes contained in a stablegel will have an interior surface oxidized species content comprisingfrom about 0.01 to less than about 1 percent relative to carbon nanotubeweight and an exterior surface oxidized species content comprises morethan about 1 to about 3 percent relative to carbon nanotube weight.

The disclosed stable gel contains surprising and unexpected properties.During formation of the stable gel, the high aspect ratio of the carbonnanotubes allows the tubes to form a three dimensional gel where thereis significant water retention but the tubes are prohibited fromagglomerating. Surprisingly, the water component of this gel may bereplaced with various other fluids such as oils, waxes, and otherhydrophobic fluids without collapsing the gel or forming strong bondsbetween carbon nanotubes by the slow addition of a hydrophobic fluid tothe existing stable gel. The interaction of the carbon nanotubes withthe hydrophobic fluid generally displaces the water bound in the gelmatrix, allowing the water to be decanted or otherwise removed from thenow largely hydrophobic gel. The process of replacing the water retainedin the stable gel with a hydrophobic fluid produces a composition ofcarbon nanotubes that is sufficiently low in water that it is suitablefor use with epoxies, rubbers, and other water sensitives matrixes, yetremains easy to disperse. The disclosed hydrophobic gel allows for thedispersion of discrete carbon nanotubes in rubber, epoxy, lithium,elastomers, polymers and/or generally hydrophobic or water sensitivematrixes without the use of surfactants which may create a loss ofconductivity, reduction in cross-linking, or loss of desirablemechanical or electrical properties in the final matrix.

General Process to Produce Discrete Carbon Nanotubes having TargetedOxidation

A mixture of 0.5% to 5% carbon nanotubes, preferably 3%, by weight isprepared with CNano grade Flotube 9000 carbon nanotubes and 65% nitricacid. While stirring, the acid and carbon nanotube mixture is heated to70 to 90 degrees C. for 2 to 4 hours. The formed oxidized carbonnanotubes are then isolated from the acid mixture. Several methods canbe used to isolate the oxidized carbon nanotubes, including but notlimited to centrifugation, filtration, mechanical expression, decantingand other solid—liquid separation techniques. The residual acid is thenremoved by washing the oxidized carbon nanotubes with an aqueous mediumsuch as water, preferably deionized water, to a pH of 3 to 4. The carbonnanotubes are then suspended in water at a concentration of 0.5% to 4%,preferably 1.5% by weight. The solution is subjected to intenselydisruptive forces generated by shear (turbulent) and/or cavitation withprocess equipment capable of producing energy densities of 106 to 108Joules/m³. Equipment that meet this specification includes but is notlimited to ultrasonicators, cavitators, mechanical homogenizers,pressure homogenizers and microfluidizers (Table 1). One suchhomogenizer is shown in U.S. Pat. No. 756,953, the disclosure of whichis incorporated herein by reference. After shear processing, theoxidized carbon nanotubes are discrete and individualized carbonnanotubes. Typically, based on a given starting amount of entangledas-received and as-made carbon nanotubes, a plurality of discreteoxidized carbon nanotubes results from this process, preferably at leastabout 60%, more preferably at least about 75%, most preferably at leastabout 95% and as high as 100%, with the minority of the tubes, usuallythe vast minority of the tubes remaining entangled, or not fullyindividualized.

Another illustrative process for producing discrete carbon nanotubesfollows: A mixture of 0. 5% to 5% carbon nanotubes, preferably 3%, byweight is prepared with CNano Flotube 9000 grade carbon nanotubes and anacid mixture that consists of 3 parts by weight of sulfuric acid (97%sulfuric acid and 3% water) and 1 part by weight of nitric acid (65-70percent nitric acid). The mixture is held at room temperature whilestirring for 3-4 hours. The formed oxidized carbon nanotubes are thenisolated from the acid mixture. Several methods can be used to isolatethe oxidized carbon nanotubes, including but not limited tocentrifugation, filtration, mechanical expression, decanting and othersolid—liquid separation techniques. The acid is then removed by washingthe oxidized carbon nanotubes with an aqueous medium, such as water,preferably deionized water, to a pH of 3 to 4. The oxidized carbonnanotubes are then suspended in water at a concentration of 0.5% to 4%,preferably 1.5% by weight. The solution is subjected to intenselydisruptive forces generated by shear (turbulent) and/or cavitation withprocess equipment capable of producing energy densities of 10⁶ to 10⁸Joules/m³. Equipment that meet this specification includes but is notlimited to ultrasonicators, cavitators mechanical homogenizers, pressurehomogenizers and microfluidizers (Table 1). After shear and/orcavitation processing, the oxidized carbon nanotubes become oxidized,discrete carbon nanotubes. Typically, based on a given starting amountof entangled as-received and as-made carbon nanotubes, a plurality ofdiscrete oxidized carbon nanotubes results from this process, preferablyat least about 60%, more preferably at least about 75%, most preferablyat least about 95% and as high as 100%, with the minority of the tubes,usually the vast minority of the tubes remaining entangled, or not fullyindividualized.

EXAMPLE 1

ENTANGLED OXIDIZED AS MWCNT—3 Hour (oMWCNT-3)

One hundred milliliters of >64% nitric acid is heated to 85 degrees C.To the acid, 3 grams of as-received, multi-walled carbon nanotubes(C9000, CNano Technology) are added. The as-received tubes have themorphology of entangled balls of wool. The mixture of acid and carbonnanotubes are mixed while the solution is kept at 85 degrees for 3 hoursand is labeled “oMWCNT-3”. At the end of the reaction period, theoMWCNT-3 are filtered to remove the acid and washed with reverse osmosis(RO) water to pH of 3-4. After acid treatment, the carbon nanotubes arestill entangled balls. The tubes are dried at 60° C. to constant weight.

EXAMPLE 2

ENTANGLED OXIDIZED AS MWCNT—6 Hour (oMWCNT-6)

One hundred milliliters of >64% nitric acid is heated to 85 degrees C.To the acid, 3 grams of as-received, multi-walled carbon nanotubes(C9000, CNano Technology) are added. The as-received tubes have themorphology of entangled balls of wool. The mixture of acid and carbonnanotubes are mixed while the solution is kept at 85 degrees for 6 hoursand is labeled “oMWCNT-6”. At the end of the reaction period, theoMWCNT-6 are filtered to remove the acid and washed with reverse osmosis(RO) water to pH of 3-4. After acid treatment, the carbon nanotubes arestill entangled balls. The tubes are dried at 60° C. to constant weight.

EXAMPLE 3

DISCRETE CARBON NANOTUBE—OXIDIZE OUTERMOST WALL (out-dMWCNT)

In a vessel, 922 kilograms of 64% nitric acid is heated to 83° C. To theacid, 20 kilograms of as received, multi-walled carbon nanotubes (C9000,CNano Technology) is added. The mixture is mixed and kept at 83° C. for3 hours. After the 3 hours, the acid is removed by filtration and thecarbon nanotubes washed with RO water to pH of 3-4. After acidtreatment, the carbon nanotubes are still entangled balls with few openends. While the outside of the tube is oxidized forming a variety ofoxidized species, the inside of the nanotubes have little exposure toacid and therefore little oxidization.. The oxidized carbon nanotubesare then suspended in RO water at a concentration of 1.5% by weight. TheRO water and oxidized tangled nanotubes solution is subjected tointensely disruptive forces generated by shear (turbulent) and/orcavitation with process equipment capable of producing energy densitiesof 10⁶ to 10⁸ Joules/m³. The resulting sample is labeled “out-dMWCNT”which represents outer wall oxidized and “d” as discrete. Equipment thatmeet this shear includes but is not limited to ultrasonicators,cavitators, mechanical homogenizers, pressure homogenizers, andmicrofluidizers (Table 1). It is believed that the shear and/orcavitation processing detangles and discretizes the oxidized carbonnanotubes through mechanical means that result in tube breaking andopening of the ends due to breakage particularly at defects in the CNTstructure which is normally a 6 member carbon rings. Defects happen atplaces in the tube which are not 6 member carbon rings. As this is donein water, no oxidation occurs in the interior surface of the discretecarbon nanotubes.

EXAMPLE 4

DISCRETE CARBON NANOTUBE—OXIDIZED OUTER AND INNER WALL (out/in-dMWCNT)

To oxidize the interior of the discrete carbon nanotubes, 3 grams of theout-dMWCNT is added to 64% nitric acid heated to 85° C. The solution ismixed and kept at temperature for 3 hours. During this time, the nitricacid oxidizes the interior surface of the carbon nanotubes. At the endof 3 hours, the tubes are filtered to remove the acid and then washed topH of 3-4 with RO water. This sample is labeled “out/in-dMWCNT”representing both outer and inner wall oxidation and “d” as discrete.

Oxidation of the samples of carbon nanotubes is determined using athermogravimetric analysis method. In this example, a TA Instruments Q50Thermogravimetric Analyzer (TGA) is used. Samples of dried carbonnanotubes are ground using a vibration ball mill. Into a tared platinumpan of the TGA, 7-15 mg of ground carbon nanotubes are added. Themeasurement protocol is as follows. In a nitrogen environment, thetemperature is ramped from room temperature up to 100° C. at a rate of10° C. per minute and held at this temperature for 45 minutes to allowfor the removal of residual water. Next the temperature is increased to700° C. at a rate of 5° C. per minute. During this process the weightpercent change is recorded as a function of temperature and time. Allvalues are normalized for any change associated with residual waterremoval during the 100° C. isotherm. The percent of oxygen by weight ofcarbon nanotubes (%Ox) is determined by subtracting the percent weightchange at 600° C. from the percent weight change at 200° C.

A comparative table (Table 2 below) shows the levels of oxidation ofdifferent batches of carbon nanotubes that have been oxidized eitherjust on the outside (Batch 1, Batch 2, and Batch 3), or on both theoutside and inside (Batch 4). Batch 1 (oMWCNT-3 as made in Example 1above) is a batch of entangled carbon nanotubes that are oxidized on theoutside only when the batch is still in an entangled form (Table 2,first column). Batch 2 (oMWCNT-6 as made in Example 2 above) is also abatch of entangled carbon nanotubes that are oxidized on the outsideonly when the batch is still in an entangled form (Table 2, secondcolumn). The average percent oxidation of Batch 1 (2.04% Ox) and Batch 2(2.06% Ox) are essentially the same. Since the difference between Batch1 (three hour exposure to acid) and Batch 2 (six hour exposure to acid)is that the carbon nanotubes were exposed to acid for twice as long atime in Batch 2, this indicates that additional exposure to acid doesnot increase the amount of oxidation on the surface of the carbonnanotubes.

Batch 3 (Out-dMWCNT as made in Example 3 above) is a batch of entangledcarbon nanotubes that were oxidized on the outside only when the batchwas still in an entangled form (Table 2, third column). Batch 3 was thenbeen made into a discrete batch of carbon nanotubes without any furtheroxidation. Batch 3 serves as a control sample for the effects onoxidation of rendering entangled carbon nanotubes into discretenanotubes. Batch 3 shows essentially the same average oxidation level(1.99% Ox) as Batch 1 and Batch 2. Therefore, Batch 3 shows thatdetangling the carbon nanotubes and making them discrete in water opensthe ends of the tubes without oxidizing the interior.

Finally, Batch 4 (Out/In-dMWCNT as made in this Example 4 herein) is abatch of entangled carbon nanotubes that are oxidized on the outsidewhen the batch is still in an entangled form, and then oxidized againafter the batch has then been made into a discrete batch of carbonnanotubes (Table 2, fourth column). Because the discrete carbonnanotubes are open ended, in Batch 4 acid enters the interior of thetubes and oxidizes the inner surface. Batch 4 shows a significantlyelevated level of average oxidation (2.39% Ox) compared to Batch 1,Batch 2 and Batch 3. The significant elevation in the average oxidationlevel in Batch 4 represents the additional oxidation of the carbonnanotubes on their inner surface. Thus, the average oxidation level forBatch 4 (2.39% Ox) is about 20% higher than the average oxidation levelsof Batch 3 (1.99% Ox). In Table 2 below, the average value of theoxidation is shown in replicate for the four batches of tubes. Thepercent oxidation is within the standard deviation for Batch 1, Batch 2and Batch 3.

TABLE 1 Energy Homogenizer Density Type Flow Regime (J-m⁻³) Stirredtanks turbulent inertial, 10³-10⁶ turbulent viscous, laminar viscousColloid mil laminar viscous, 10³-10⁸ turbulent viscous Toothed—discturbulent viscous 10³-10⁸ disperser High pressure turbulent inertial,10⁶-10⁸ homogenizer turbulent viscous, cavitation inertial, laminarviscous Ultrasonic probe cavitation inertial 10⁶-10⁸ Ultrasonic jetcavitation inertial 10⁶-10⁸ Microfluidization turbulent inertial,10⁶-10⁸ turbulent viscous Membrane and Injection spontaneous Lowmicrochannel transformation based 10³ Excerpted from Engineering Aspectsof Food Emulsification and Homogenization, ed. M. Rayner and P. Dejmek,CRC Press, New York 2015.

TABLE 2 Percent oxidation by weight of carbon nanotubes. Batch 3: Batch4: Difference *% Batch 1: Batch 2: Out- Out/In- in % Ox difference inoMWCNT-3 oMWCNT-6 dMWCNT dMWCNT (Batch 4 − % Ox (Batch % Ox % Ox % Ox %Ox Batch 3) 4 v Batch 3) 1.92 1.94 2.067 2.42 0.353 17% 2.01 2.18 1.8972.40 0.503 26.5%  2.18 NM 2.12 2.36 0.24 11% 2.05 NM 1.85 NM n/a n/aAverage 2.04 2.06 1.99 2.39 0.4 20% St. Dev. 0.108  0.169 0.130  0.030n/a n/a NM = Not Measured *% difference between interior and exterioroxidation surfaces (Batch 4 v Batch 3) = (((outside % oxidation) −(inside % oxidation)) ÷ (outside % oxidation)) × 100

An illustrative process to form a composition comprising discrete carbonnanotubes in a plasticizer is to first select a plurality of discretecarbon nanotubes having an average aspect ratio of from about 10 toabout 500, and an oxidative species content total level from about 1 toabout 15% by weight. Then the discrete carbon nanotubes are suspendedusing shear in water at a nanotube concentration from about 1% to about10% by weight to form the nanotube water slurry. The slurry is thenmixed with at least one plasticizer at a temperature from about 30° C.to about 100° C. for sufficient time that the carbon nanotubes migratefrom the water to the plasticizer to form a water nanotube/plasticizermixer. The mixture can comprise from 70% to about 99.9% water. The bulkof the water is separated from the mixture by filtration, decanting orother means of mechanical separation. The filtered material can containfrom about 50% to about 10% water. The filtered material is then driedat a temperature from about 40° C. to about 120° C. to form an anhydrousnanotube/plasticizer mixture with less than 3% water, most preferablyless than 0.5% water by weight and for some applications 0% water byweight.

EXAMPLE 5

A concentrate of discrete carbon nanotubes in water with only theexterior wall oxidized as in Example 3 is diluted to a 2% by weight indeionized water. The slurry is heated to 40° C. while stirring with anoverhead stirrer at 400 rpm. For every gram of discrete carbonnanotubes, 4 grams of TOTM (trioctyl trimellitate) from Sigma Aldrich isadded to the stirring mixture. For 4 hours, the mixture is stirred at750 rpm and kept at 40° C. During this time, the oil and discrete carbonnanotubes floats to the top, leaving clear water at the bottom. Whenthis occurs, the water is separated from the TOTM/carbon nanotubemixture by filtration. The TOTM and discrete carbon nanotubes are driedin a forced air convection oven at 70° C. until residual water isremoved. The result is a flowable powder. The concentration of discretecarbon nanotubes is determined by thermogravimetric means and found tobe 20% discrete carbon nanotubes and 80% TOTM.

EXAMPLE 6

The discrete carbon nanotubes and plasticizer composition of Example 5comprising 20% discrete carbon nanotubes and 80% TOTM (trioctyletrimellitate) is added at concentrations of 2 parts per hundred resin(phr) and 3 parts per hundred resin (phr) to a nitrile rubberformulation (Table 3). The oil concentration of the compounds isadjusted to compensate for the additional oil from the composition ofthis invention. The compound is then cured into plaques for testing.Constrained tear testing is performed using an Instron tensiometer.Constrained tear samples are punched out using a die, making a rectangle1.5 inches by 1 inch by 1 inch with a specimen-centered notch ½ inchlong, sliced perpendicular to the longest dimension. The specimen isgripped equal distance from the notch and pulled by the Instron. Shearstrain and stress is recorded and the area under the stress-strain curvefrom strain zero to the final failure is measured. This area is thetotal tear energy. The results in Table 4 indicate that an increase intear strength is imparted by the discrete carbon nanotubes.

TABLE 3 2 phr 3 phr Ingredient Control dCNT dCNT Nitrile Rubber (Nipol3640S) 100 100 100 20% dCNT in TOTM 0 10 15 N774 Carbon Black 80 75 75Polyester sebacate plasticizer 15 7 3 (Paraplex G-25) Coumarone IndeneResin 10 10 10 (Cumar P25) Stearic Acid 1 1 1 Zinc Oxide (Kadox 911) 5 55 Antioxidant (Vanox CDPA) 2 2 2 Antioxidant (Santoflex 6PPD) 2 2 2 Highmolecular fatty acid 2 2 2 esters (Struktol WB212) Accelerator DTDM 2 22 Accelerator (Morfax) 2.26 2.26 2.26 Accelerator TMTM 1 1 1

TABLE 4 Constrained Description Tear (psi) Control 482 2 phr dCNT 537 3phr dCNT 574

EXAMPLE 7

The discrete carbon nanotubes and plasticizer composition of Example 5comprising 20% discrete carbon nanotubes and 80% TOTM (trioctyletrimellitate) is added at concentrations 3 parts per hundred resin (phr)to a nitrile rubber formulation (Table 5). The oil concentration of thecompound is adjusted to compensate for the additional oil from thecomposition of this invention so that all formulations have equivalentoil concentrations. A comparative compound is prepared with carbonnanotubes as received (Flotube C9000, CNano) (Table 5). Carbon blackcontent is adjusted so that the measured hardness is the same for thethree samples. The Shore A hardness is 67 for the control and 67 for the3 phr CNT of this invention and 68 for the 3 phr “As is” carbonnanotubes (C9000). The constrained tear is measured as described inExample 6. The discrete carbon nanotubes and oil composition (dCNT) ofthis invention have higher total tear energy than the entangled carbonnanotubes (C9000) and the control. The tear energy of entangled carbonnanotubes, C9000, is worse than the control. (Table 6)

TABLE 5 3 phr 3 phr Ingredient Control dCNT C9000 Nitrile Rubber (Nipol3640S) 100 100 100 20% dCNT in TOTM 0 15 0 MWCNT as received 0 0 3(C9000, CNano) N774 Carbon Black 80 75 75 Polyester sebacate plasticizer15 3 15 (Paraplex G-25) Coumarone Indene Resin 10 10 10 (Cumar P25)Stearic Acid 1 1 1 Zinc Oxide (Kadox 911) 5 5 5 Antioxidant (Vanox CDPA)2 2 2 Antioxidant (Santoflex 6PPD) 2 2 2 High molecular fatty acid 2 2 2esters (Struktol WB212) Accelerator DTDM 2 2 2 Accelerator (Morfax) 2.262.26 2.26 Accelerator TMTM 1 1 1

TABLE 6 Constrained Description Tear (psi) Control 482 3 phr dCNT 574 3phr C9000 394

It is known to those practiced in the art that the addition of filler toa rubber compound will increase the viscosity of the compound.Unexpectedly, the addition of discrete carbon nanotube and oil mixturefrom Example 7 did not increase the viscosity but instead decreasedviscosity, while the entangled carbon nanotubes of Example 7 (C9000)increased the viscosity. The viscosity is measured using a MooneyRheometer at 125° C. The initial viscosity measured is descriptive ofthe processibility of the compound. The compound containing the discretecarbon nanotubes of this invention and described in Example 7 is foundto be equal to the control while the compound containing the entangledcarbon nanotubes (C9000) is found to be higher than the control (Table7).

TABLE 7 Minimum Mooney Viscosity ML Description (1 + 30) Control 23.1 3phr dCNT 23.1 3 phr C9000 26.6

Disclosed embodiments may also relate to a composition useful fortreating and/or remediating contaminated soil, groundwater and/orwastewater by treating, removing, modifying, sequestering, targetinglabeling, and/or breaking down at least a portion of any dry cleaningcompounds and related compounds such as perchloroethene (PCE),trichloroethene (TCE), 1,2-dichloroethene (DCE), vinyl chloride, and/orethane. Embodiments may also relate to compounds useful for treating,removing, modifying, sequestering, targeting labeling, and/or breakingdown at least a portion of any oils, hazardous or undesirable chemicals,and other contaminants. Disclosed embodiments may comprise a pluralityof discrete carbon nanotubes, wherein the discrete carbon nanotubescomprise an interior and exterior surface. Each surface may comprise aninterior surface oxidized species content and/or an exterior surfaceoxidized species content. Embodiments may also comprise at least onedegradative or otherwise chemically active molecule that is attached oneither the interior or the exterior surface of the plurality of discretecarbon nanotubes. Such embodiments may be used in order to deliver knowndegradative and/or chemically active molecules to the location of anycontaminated soil, groundwater and/or wastewater.

Addition of Payload Molecule

Aqueous solubility of drug substances is an important parameter inpre-formulation studies of a drug product. Several drugs are sparinglywater-soluble and pose challenges for formulation and doseadministration. Organic solvents or oils and additional surfactants tocreate dispersions can be used. If the payload molecule is easilydissolved or dispersed in an aqueous media, the filter cake need not bedried. If the payload molecule is not easily dissolved or dispersed inaqueous media, the filter cake is first dried at 80° C. in vacuo toconstant weight. The payload molecule in the liquid media at the desiredconcentration is added to the discrete carbon nanotubes and allowedseveral hours to equilibrate within the tube cavity. The mixture is thenfiltered to form a cake, less than about 1 mm thickness, then the bulkof the payload solution not residing within the tubes are removed byhigh flow rate filtration. The rate of filtration is selected so thatlittle time is allowed for the payload molecules to diffuse from thetube cavity. The filter cake plus payload drug is then subjected to anadditional treatment if desired to attach a large molecule such anaqueous solution of a biopolymer, an amino acid, protein or peptide.

EXAMPLE 8

A calibration curve for the UV absorption of niacin as a function of theconcentration of niacin in water was determined. A solution was preparedby mixing 0.0578 grams of discrete functionalized carbon nanotubes ofthis invention with 0.0134 grams of niacin in 25 ml of water [0.231grams niacin/gram of carbon nanotube]. The tubes were allowed to settleand an aliquot of the fluid above the tubes removed hourly. The UV-visabsorption of this aliquot was measured and the resulting amount ofniacin in the solution recorded. The amount of niacin in solutionstabilized after 6 hours. A final sample was taken 20 hours aftermixing. The difference between the amounts of niacin remaining in thesolution and the original amount was determined to be the amount ofniacin associated with the discrete functionalized carbon nanotubes. Itwas found that 0.0746 grams of niacin associated with each gram ofcarbon nanotubes. The total amount of niacin absorbed by the carbonnanotubes was 0.0043 grams. Assuming an average carbon nanotube lengthof 1000 nm, external diameter of 12 nm and internal diameter of 5 nm,the available volume within the tube is 0.093 cm3 per gram of carbonnanotubes. Since the density of niacin is 1.473 g/cm3, then the maximumamount of niacin that can fit in the tubes is 0.137 grams. Therefore,the measured absorption of 0.0746 g niacin/g CNT amount could beconfined to the interior of the tube.

EXAMPLE 9

A poly (vinyl alcohol), PVOH, is sufficiently large (30 kDa-70 kDa) thatit cannot be absorbed internally in a carbon nanotube. PVOH is used as asurfactant for carbon nanotubes because it associates and wraps theexterior of the carbon nanotube. In this experiment, PVOH was added to amixture of 0.0535 g of carbon nanotubes and 0.0139 g niacin (0.26 gramsniacin to 1 gram carbon nanotubes) in 25 ml water. This was allowed torest overnight. Using the UV-vis technique of Example 1, the amount ofniacin associated with the carbon nanotubes was determined to be 0.0561grams niacin per gram of carbon nanotubes, less than the 0.0746 grams inexample 1. The total amount of niacin absorbed was 0.003 grams.

Calculations were made assuming carbon nanotube length of 1000 nm,external diameter of 12 nm and internal diameter of 5 nm. Given thedensity of PVOH is 1.1 g/cm3 and the ratio of PVOH to carbon nanotubeswas 0.23 to 1, the average layer thickness of PVOH on the carbonnanotube is 0.6 nm. Therefore there is sufficient PVOH to encapsulatethe carbon nanotube and displace any niacin on the surface of the tubeand the measured amount of 0.0561 grams of niacin per gram of carbonnanotubes is in the interior of the carbon nanotube.

In another example the discrete functionalized carbon nanotubes can bedispersed in a polymeric matrix, for example polyethylene oxide, in themelt or in a solution and the payload molecule added.

TABLE 8 Lengths (nm) Condition 1 Condition 2 Condition 3 Mean 424 487721 Standard Error 25.3 34.9 50 Median 407 417.0 672 Standard Deviation177 281 315 Sample Variance 31461 79108 99418 Kurtosis −0.83 1.5 −0.02Skewness 0.03 1.2 0.64 Range 650 1270.0 1364 Minimum 85 85.0 161 Maximum735 1355 1525

Condition 1 is an example of a narrow distribution with low mean length.Condition 2 is an example of broad distribution with low mean length.Condition 3 is an example of high mean length and broad distribution.

To determine tube lengths, a sample of tubes is diluted in isopropylalcohol and sonicated for 30 minutes. It is then deposited onto a silicawafer and images are taken at 15 kV and 20,000 x magnification by SEM.Three images are taken at different locations. Utilizing the JEOLsoftware (included with the SEM) a minimum of 2 lines are drawn acrosson each image and measure the length of tubes that intersect this line.

Skewness is a measure of the asymmetry of a probability distribution. Apositive value means the tail on the right side of the distributionhistogram is longer than the left side and vice versa. Positive skewnessis preferred which indicates means more tubes of long lengths. A valueof zero means a relatively even distribution on both sides of the meanvalue.Kurtosis is the measure of the shape of the distribution curve andis generally relative to a normal distribution. Both skewness andkurtosis are unitless.

The following table shows representative values of discrete carbonnanotubes diameters:

TABLE 9 Diameter (unrelated to condition above) Mean diameter (nm*) 12.5Median diameter (nm) 11.5 Kurtosis 3.6 Skewness 1.8 Calculated aspectratio 34 39 58 (L/D) *nm = nanometer

A small sample of the filter cake is dried in vacuum at 100° C. for 4hours and a thermogravimetric analysis performed at 10° C./min heatingrate in nitrogen from 100° C. to 600° C. The amount of oxidized specieson the fiber is taken as the weight loss between 200 and 600° C. Thedispersion of individual tubes (discrete) is also determined by UVspectroscopy. Water is added to the wet cake to give a 0.5% weightcarbon nanotube suspension, then sodium dodecylbenzene sulfonic acid isadded at a concentration of 1.5 times the mass of oxidized carbonnanotubes. The solution is sonicated for 30 minutes using a sonicatorbath then diluted to a concentration of 2.5×10-5 g carbon nanotubes/ml.The carbon nanotubes will give a UV absorption at 500 nm of at least 1.2absorption units.

The improvement in flow processibility of the compositions can bedetermined using a rheometer, for example, utilizing concentriccylinders with a well-defined geometry to measure a fluid's resistanceto flow and determine its viscous behavior. While relative rotation ofthe outer cylinder causes the composition to flow, its resistance todeformation imposes a shear stress on the inner wall of the cup,measured in units of Pa.

EXAMPLE 10

A stable gel or wet cake containing discrete carbon nanotubes may besurprisingly and unexpectedly created by soaking as manufactured CNanograde Flotube 9000 carbon nanotubes in deionized water for 5 hourswithout the use of a surfactant. The carbon nanotubes may then be vacuumfiltered to form a stable gel containing approximately 16.8% totalsolids. The terms “stable gel” and “wet cake” are used interchangeablyherein whether or not any cross-linking is present. These terms indicatethat the resultant stable gel or wet cake has a relatively high watercontent (80-99% fluid or liquid (usually water)) and remain dry to thetouch and pourable as if little to no water was present in thecomposition at all. Alternatively, a slurry of oxidized C9000 carbonnanotubes may be filtered and washed to 3.9 pH and then vacuum filteredto form a stable gel containing approximately 15.8% total solids.Finally a preformed slurry of discrete carbon nanotubes may be vacuumfiltered to form a stable gel with approximately 5.4% total solids.

Embodiments

Embodiments disclosed in this application include:

-   -   1. A composition comprising a plurality of discrete carbon        nanotubes, wherein the discrete carbon nanotubes comprise an        interior and exterior surface, each surface comprising an        interior surface oxidized species content and an exterior        surface oxidized species content, wherein the interior surface        oxidized species content differs from the exterior surface        oxidized species content by at least 20%, and as high as 100%.    -   2. The composition of embodiment 1 wherein the interior surface        oxidized species content is less than the exterior surface        oxidized species content.    -   3. The composition of embodiment 1 wherein the interior surface        oxidized species content is up to 3 weight percent relative to        carbon nanotube weight, preferably from about 0.01 to about 3        weight percent relative to carbon nanotube weight, more        preferably from about 0.01 to about 2, most preferably from        about 0.01 to about 1.    -   4. The composition of embodiment 1 wherein the exterior surface        oxidized species content is from about 1 to about 6 weight        percent relative to carbon nanotube weight, preferably from        about 1 to about 4, more preferably from about 1 to about 2.    -   5. The composition of embodiment 1 wherein the interior and        exterior surface oxidized species content totals from about 1 to        about 9 weight percent relative to carbon nanotube weight.    -   6. A composition comprising a plurality of discrete carbon        nanotubes, wherein the discrete carbon nanotubes comprise an        interior and exterior surface, each surface comprising an        interior surface and an exterior surface oxidized species        content, wherein the interior surface oxidized species content        comprises from about 0.01 to less than about 1 percent relative        to carbon nanotube weight and the exterior surface oxidized        species content comprises more than about 1 to about 3 percent        relative to carbon nanotube weight.    -   7. The composition of embodiment 6 wherein the discrete carbon        nanotubes comprise a plurality of open ended tubes.    -   8. The composition of embodiment 6 wherein the plurality of        discrete carbon nanotubes comprise a plurality of open ended        tubes.    -   9. The composition of embodiment 1 wherein the discrete carbon        nanotubes comprise a plurality of open ended tubes.    -   10. Use of the composition of embodiment 1 as an ion transport.    -   11. Use of the composition of embodiment 1 as targeting,        sequestering and labeling agent in ground water remediation.    -   12. A sensor comprising the composition of embodiment 1 or        embodiment 6.    -   13. A drug delivery or controlled release formulation comprising        the composition of embodiment 1 or embodiment 6.    -   14. A battery comprising the composition of embodiment 1 or        embodiment 6.    -   15. A formulation comprising the composition of embodiment 1 or        embodiment 6 further comprising an epoxy, a polyurethane, or an        elastomer.    -   16. The composition of embodiment 1 or embodiment 6 further        comprising at least one hydrophobic material in contact with at        least one interior surface.    -   17. The composition of embodiment 1 or embodiment 6 wherein the        inner and outer surface oxidation difference is at least about        0.2 weight percent.    -   18. The composition of embodiment 1 or embodiment 6 and at least        one plasticizer, wherein the discrete carbon nanotubes have an        aspect ratio of about 10 to about 500, and wherein the carbon        nanotubes have an oxidation level of about 1 to 3 percent by        weight of carbon nanotubes.    -   19. The composition of embodiment 18 wherein the composition        comprises from about 10 weight percent to about 90 weight,        preferably from about 10 weight percent to about 40 weight        percent, discrete carbon nanotubes.    -   20. The composition of embodiment 18 wherein the oxygenated        species is selected from the group consisting of carboxylic        acids, phenols, aldehydes, ketones, ether linkages, and        combinations thereof.    -   21. The composition of embodiment 18 wherein the total        oxygenated species content of the interior surface and exterior        surface comprises from about 1% to 15% by weight of the carbon        nanotubes.    -   22. The composition of embodiment 18, wherein the plasticizer is        selected from the group consisting of dicarboxylic/tricarboxylic        esters, timellitates, adipates, sebacates, maleates, glycols and        polyethers, polymeric plasticizers, bio-based plasticizers, and        mixtures thereof.

23. The composition of embodiment 18, wherein the plasticizer is aprocess oil selected from the group consisting of naphthenic oils,paraffin oils, paraben oils, aromatic oils, vegetable oils, seed oils,and mixtures thereof.

-   -   24. The composition of embodiment 23 having a viscosity about        the same as, or less than, an identical composition comprising        the same elements in the same ratios, except the carbon        nanotubes are not discrete but are entangled as-manufactured.    -   25. The composition of embodiment 18, wherein the plasticizer is        a water immiscible solvent selected from the group consisting of        xylene, pentane, methylethyl ketone, hexane, heptane, ethyl        actetate, ethers, dicloromethane, dichloroethane, cyclohexane,        chloroform, carbon tetrachloride, butyl acetate butanol,        benzene, and mixtures thereof.    -   26. The composition of embodiment 18, further comprising an        inorganic filler selected from the group consisting of silica,        nano-clays, carbon black, graphene, glass fibers, and mixtures        thereof.    -   27. The composition of embodiment 18 in the form of free flowing        particles.    -   28. A process to make the composition of embodiment 18,        comprising the steps of: a) selecting a plurality of discrete        carbon nanotubes having an average aspect ratio of from about 10        to about 500, and an oxidative species content total level from        about 1 to about 15% by weight, b) suspending the discrete        carbon nanotubes in an aqueous medium at a nanotube        concentration from about 1% to about 10% by weight to form an        aqueous medium/nanotube slurry, c) mixing the carbon        nanotube/aqueous medium slurry with at least one plasticizer at        a temperature from about 30° C. to about 100° C. for sufficient        time that the carbon nanotubes migrate from the aqueous medium        to the plasticizer to form a wet nanotube/plasticizer        mixture, e) separating the aqueous medium from the wet carbon        nanotube/plasticizer mixture to form a dry nanotube/plasticizer        mixture, and f) removing residual aqueous medium from the dry        nanotube/plasticizer mixture by drying from about 40° C. to        about 120° C. to form an anhydrous nanotube/plasticizer mixture.    -   29. The composition of embodiment 18, wherein the composition is        further mixed with at least one rubber.    -   30. The composition of embodiment 29, wherein the rubber is a        natural or synthetic rubber selected from the group consisting        of natural rubbers, polyisobutylene, polybutadiene and        styrene-butadiene rubber, butyl rubber, polyisoprene,        styrene-isoprene rubbers, styrene-isoprene rubbers, ethylene,        propylene diene rubbers, silicones, polyurethanes,        polyester-polyethers, hydrogenated and non-hydrogenated nitrile        rubbers, halogen modified elastomers, fluoro-elastomers, and        combinations thereof.    -   31. The composition of embodiment 18, wherein the composition        further comprises at least one thermoplastic polymer, at least        one thermoplastic elastomer, or combinations thereof.    -   32. The composition of embodiment 18, wherein the composition        further comprises at least one thermoset polymer, preferably        epoxy, or polyurethane.    -   33. A composition useful for treating groundwater that has been        contaminated with dry-cleaning compounds comprising a plurality        of discrete carbon nanotubes, wherein the discrete carbon        nanotubes comprise an interior and exterior surface, each        surface comprising an interior surface oxidized species content        and an exterior surface oxidized species content, and at least        one degradative molecule that is attached on the interior or        exterior surface of the plurality of discrete carbon nanotubes.    -   34. In a composition comprising a plurality of discrete carbon        nanotubes, wherein the discrete carbon nanotubes comprise an        interior and exterior surface, the interior surface comprising        an interior surface oxidized species content and the exterior        surface comprising an exterior surface oxidized species content,        the improvement comprising: a stable gel composition wherein the        plurality of discrete carbon nanotubes are coated with a fluid        which prevents the carbon nanotubes from agglomerating, the        stable gel comprising from about 1 to about 20% solids by        weight.    -   35. The improvement of embodiment 34, wherein the stable gel        comprises from about 2 to about 15% solids by weight.    -   36. The improvement of embodiment 34, wherein the stable gel        comprises from about 3 to about 7% solids by weight.    -   37. The improvement of embodiment 34, wherein the wherein the        interior surface oxidized species content differs from the        exterior surface oxidized species content by at least about 20%,        and as high as 100%.    -   38. The improvement of embodiment 34, wherein the interior        surface oxidized species content comprises from about 0.01 to        less than about 1 percent relative to carbon nanotube weight and        the exterior surface oxidized species content comprises more        than about 1 to about 3 percent relative to carbon nanotube        weight.    -   39. The improvement of embodiment 34, wherein the stable gel is        substantially free from surfactants.    -   40. The improvement of embodiment 34, wherein the fluid        comprises water.    -   41. The improvement of embodiment 34, wherein the fluid        comprises a hydrophobic fluid.    -   42. In a composition comprising a plurality of discrete carbon        nanotubes, wherein the discrete carbon nanotubes comprise an        interior and exterior surface, the interior surface comprising        an interior surface oxidized species content and the exterior        surface comprising an exterior surface oxidized species content,        the improvement comprising a first species of magnetic particles        bound to the discrete carbon nanotubes.    -   43. The improvement of embodiment 42, wherein the magnetic        particles are bound to the exterior of the carbon nanotubes.    -   44. The improvement of embodiment 42, wherein the magnetic        particles comprise from about 0.01% to about 10% relative to the        carbon weight.    -   45. The improvement of embodiment 43, wherein the carbon        nanotubes bound to magnetic particles may be directed or        influenced by the application of a magnetic field.    -   46. The improvement of embodiment 42, further comprising a        second species of magnetic particle.    -   47. In a composition comprising a plurality of discrete carbon        nanotubes, wherein the discrete carbon nanotubes comprise an        interior and exterior surface, the improvement comprising: the        interior surface comprising an interior surface oxidized species        content and the exterior surface comprising an exterior surface        oxidized species content, wherein the interior surface oxidized        species content differs from the exterior surface oxidized        species content by at least 20%, and as high as 100%.    -   48. The improvement of embodiment 47, wherein the plurality of        discrete carbon nanotubes comprises a plurality of open ended        tubes.    -   49. The improvement of embodiment 47m 14, wherein the interior        surface oxidized species content is less than the exterior        surface oxidized species content.    -   50. The improvement of embodiment 47, wherein the interior        surface oxidized species content comprises up to 3 weight        percent relative to carbon nanotube weight.    -   51. The improvement of embodiment 47wherein the exterior surface        oxidized species content comprises from about 1 to about 6        weight percent relative to carbon nanotube weight.    -   52. The improvement of embodiment 47, wherein the composition is        further mixed with at least one rubber.    -   53. The improvement of claim 14, wherein the oxygenated species        is selected from the group consisting of carboxylic acids,        phenols, aldehydes, ketones, ether linkages, and combinations        thereof.

We claim:
 1. In a composition comprising a plurality of discrete carbonnanotubes, wherein the discrete carbon nanotubes comprise an interiorand exterior sidewall surface, the improvement comprising: the interiorsidewall surface comprising an interior surface oxidized species contentand the exterior sidewall surface comprising an exterior surfaceoxidized species content, wherein the interior surface oxidized speciescontent differs from the exterior surface oxidized species content by atleast 20%, and as high as 100% and wherein the composition furthercomprises a species of electro-magnetic active particles.
 2. Theimprovement of claim 1, wherein the species of electro-magnetic activeparticles are bound to the exterior of the carbon nanotubes.
 3. Theimprovement of claim 1, wherein the species of electro-magnetic activeparticles comprise from about 0.01% to about 10% of the compositionrelative to the carbon weight.
 4. The improvement of claim 1, whereinthe carbon nanotubes may be directed or influenced by the application ofa magnetic field.
 5. The improvement of claim 2, wherein the carbonnanotubes bound to the species of electro-magnetic active particles maybe directed or influenced by the application of a magnetic field.
 6. Theimprovement of claim 1, further comprising a second species ofelectro-magnetic active particles.
 7. The improvement of claim 2,further comprising a second species of electro-magnetic activeparticles.
 8. The improvement of claim 1, wherein the plurality ofdiscrete carbon nanotubes comprises a plurality of open ended tubes. 9.The improvement of claim 1, wherein the interior surface oxidizedspecies content is less than the exterior surface oxidized speciescontent.
 10. The improvement of claim 2, wherein the interior surfaceoxidized species content is less than the exterior surface oxidizedspecies content.
 11. The improvement of claim 1, wherein the interiorsurface oxidized species content comprises up to 3 weight percentrelative to carbon nanotube weight.
 12. The improvement of claim 2,wherein the interior surface oxidized species content comprises up to 3weight percent relative to carbon nanotube weight
 13. The improvement ofclaim 1, wherein the exterior surface oxidized species content comprisesfrom about 1 to about 6 weight percent relative to carbon nanotubeweight.
 14. The improvement of claim 2, wherein the exterior surfaceoxidized species content comprises from about 1 to about 6 weightpercent relative to carbon nanotube weight.
 15. The improvement of claim1, wherein the composition further comprises at least one rubber. 16.The improvement of claim 1, wherein the composition further comprises atleast one payload molecule.
 17. The improvement of claim 2, wherein thecomposition further comprises at least one payload molecule.
 18. Theimprovement of claim 1, wherein the oxidized species is selected fromthe group consisting of carboxylic acids, phenols, aldehydes, ketones,ether linkages, and combinations thereof.
 19. The improvement of claim1, wherein the composition further comprises carbon black.
 20. Theimprovement of claim 1, wherein the composition further comprises carbonnanotubes that are at least partially entangled.